If it takes more than 4-6 hours to drive there, high speed rail is the clear choice. I'm someone who has been on several 10+ hour road trips, and driving for more than a few hours at a time sucks. You waste up to an entire day just driving. Even if it does take the same amount of time, it'd be nice to nap or read a book in that time instead of focusing on just driving. It's mentally and physically exhausting.
Especially I-70 in western Kansas and eastern Colorado.